Growth factors and the gastrointestinal tract

Characterization and Expression Analysis of Mollusk-like Growth Factor: A Secreted Protein Involved in Pacific Abalone Embryonic and Larval Development

Growth factors are mostly secreted proteins that play key roles in an organism's biophysical processes through binding to specific receptors on the cell surface. The mollusk-like growth factor (MLGF) is a novel cell signaling protein in the adenosine deaminase-related growth factor (ADGF) subfamily. In this study, the MLGF gene was cloned and characterized from the digestive gland tissue of Pacific abalone and designated as Hdh-MLGF. The transcribed full-length sequence of Hdh-MLGF was 1829 bp long with a 1566 bp open reading frame (ORF) encoding 521 amino acids. The deduced amino acid sequence contained a putative signal peptide and two conserved adenosine deaminase domains responsible for regulating molecular function. Fluorescence in situ hybridization localized Hdh-MLGF in the submucosa layer of digestive tubules in the digestive gland. The mRNA expression analysis indicated that Hdh-MLGF expression was restricted to the digestive gland in the adult Pacific abalone. However, Hdh-MLGF mRNA expressions were observed in all stages of embryonic and larval development, suggesting Hdh-MLGF might be involved in the Pacific abalone embryonic and larval development. This is the first study describing Hdh-MLGF and its involvement in the Pacific abalone embryonic and larval development.

Supplementation of Diets With Bovine Colostrum Influences Immune and Gut Function in Kittens

In its early life a kitten faces many significant events including separation from its mother, re-homing and vaccination. The kitten is also slowly adapting to their post-weaning diet. Recent advances in companion animal nutrition have indicated that functional ingredients such as colostrum can help support the immune system and gastrointestinal health. Here we report for the first time the effect of feeding a diet containing 0.1% spray dried bovine colostrum (BC) to growing kittens on gut-associated lymphoid (GALT) tissue responses, systemic immune responses, and on intestinal microbiota stability. BC supplementation induced increased faecal IgA expression, and a faster and stronger antibody response to a rabies vaccine booster, indicative of better localised and systemic immune function, respectively. BC supplementation also helped to maintain kittens' intestinal microbiota stability in the face of a mildly challenging life event. These results show that BC supplementation can help strengthen the immune system and enhance the gut microbiota stability of growing kittens.

Mucins as multifunctional building blocks of biomaterials

Mucins glycoproteins are emerging as a multifunctional building block for biomaterials with diverse applications in chemistry and biomedicine.

Parenteral Nutrition and Intestinal Failure

Severe short bowel syndrome (SBS) is a major cause of chronic (Type 3) intestinal failure (IF) where structural and functional changes contribute to malabsorption and risk of micronutrient deficiencies. Chronic IF may be reversible, depending on anatomy and intestinal adaptation, but most patients require long-term nutritional support, generally in the form of parenteral nutrition (PN). SBS management begins with dietary changes and pharmacologic therapies taking into account individual anatomy and physiology, but these are rarely sufficient to avoid PN. New hormonal therapies targeting intestinal adaptation hold promise. Surgical options for SBS including intestinal transplant are available, but have significant limitations. Home PN (HPN) is therefore the mainstay of treatment for severe SBS. HPN involves chronic administration of macronutrients, micronutrients, fluid, and electrolytes via central venous access in the patient's home. HPN requires careful clinical and biochemical monitoring. Main complications of HPN are related to venous access (infection, thrombosis) and metabolic complications including intestinal failure associated liver disease (IFALD). Although HPN significantly impacts quality of life, outcomes are generally good and survival is mostly determined by the underlying disease. As chronic intestinal failure is a rare disease, registries are a promising strategy for studying HPN patients to improve outcomes.

Cytokines and growth factors in the developing intestine and during necrotizing enterocolitis

Cytokines and growth factors play diverse roles in the uninflamed fetal/neonatal intestinal mucosa and in the development of inflammatory bowel injury during necrotizing enterocolitis (NEC). During gestational development and the early neonatal period, the fetal/premature intestine is exposed to high levels of many "inflammatory" cytokines and growth factors, first via swallowed amniotic fluid in utero and then, after birth, in colostrum and mother's milk. This article reviews the dual, seemingly counter-intuitive roles of cytokines, where these agents play a "trophic" role and promote maturation of the uninflamed mucosa, but can also cause inflammation and promote intestinal injury during NEC.

An undigested gliadin peptide activates innate immunity and proliferative signaling in enterocytes: the role in celiac disease

BACKGROUND

On ingestion of gliadin, the major protein component of wheat and other cereals, the celiac intestine is characterized by the proliferation of crypt enterocytes with an inversion of the differentiation/proliferation program. Gliadins and A-gliadin peptide P31-43, in particular, act as growth factors for crypt enterocytes in patients with celiac disease (CD). The effects of gliadin on crypt enterocyte proliferation and activation of innate immunity are mediated by epidermal growth factors (EGFs) and innate immunity mediators [interleukin 15 (IL15)].

OBJECTIVE

The aim of this study was to determine the molecular basis of proliferation and innate immune response to gliadin peptides in enterocytes.

DESIGN

The CaCo-2 cell line was used to study EGF-, IL15-, and P31-43-induced proliferation. Silencing messenger RNAs and blocking EGF receptor and IL15 antibodies have been used to study proliferation in CaCo-2 cells and intestinal biopsy samples from patients with CD and control subjects.

RESULTS

In the CaCo-2 cell model, IL15 and EGF cooperated to induce proliferation in intestinal epithelial cells at both the transcriptional and posttranscriptional levels, and the respective receptors interacted to activate each other's signaling. In addition, the effects of the P31-43 peptide on CaCo-2 cell proliferation and downstream signaling were mediated by cooperation between EGF and IL15. The increased crypt enterocyte proliferation in intestinal biopsy samples from patients with CD was reduced by EGF receptor and IL15 blocking antibodies only when used in combination.

CONCLUSIONS

EGF receptor/IL15R-α cooperation regulates intestinal epithelial cell proliferation induced by EGF, IL15, and the gliadin peptide P31-43. Increased proliferation of crypt enterocytes in the intestine of CD patients is mediated by EGF/IL15 cooperation.

Prenatal and Postnatal Epigenetic Programming: Implications for GI, Immune, and Neuronal Function in Autism

Although autism is first and foremost a disorder of the central nervous system, comorbid dysfunction of the gastrointestinal (GI) and immune systems is common, suggesting that all three systems may be affected by common molecular mechanisms. Substantial systemic deficits in the antioxidant glutathione and its precursor, cysteine, have been documented in autism in association with oxidative stress and impaired methylation. DNA and histone methylation provide epigenetic regulation of gene expression during prenatal and postnatal development. Prenatal epigenetic programming (PrEP) can be affected by the maternal metabolic and nutritional environment, whereas postnatal epigenetic programming (PEP) importantly depends upon nutritional support provided through the GI tract. Cysteine absorption from the GI tract is a crucial determinant of antioxidant capacity, and systemic deficits of glutathione and cysteine in autism are likely to reflect impaired cysteine absorption. Excitatory amino acid transporter 3 (EAAT3) provides cysteine uptake for GI epithelial, neuronal, and immune cells, and its activity is decreased during oxidative stress. Based upon these observations, we propose that neurodevelopmental, GI, and immune aspects of autism each reflect manifestations of inadequate antioxidant capacity, secondary to impaired cysteine uptake by the GI tract. Genetic and environmental factors that adversely affect antioxidant capacity can disrupt PrEP and/or PEP, increasing vulnerability to autism.

The effect of bevacizumab on colon anastomotic healing in rats

PURPOSE

The aim of the study was to investigate the effect of angiogenesis inhibition by bevacizumab, a monoclonal anti-vascular endothelial growth factor (VEGF) antibody, on the healing process of colonic anastomoses in rats, assessing some specific involved factors. This new agent is used mainly in metastatic colorectal cancer. The angiogenesis plays an important role in both wound healing and metastatic invasion and spread of malignant cells. There has not been any evidence assessing the optimal time for its safe use in operated patients.

MATERIALS AND METHODS

Forty Wistar rats were randomly allocated into four equal groups. A colonic anastomosis was performed in all rats. Half of them received intraoperatively a single dose of bevacizumab 5 mg/body weight and the rest received placebo. The animals were sacrificed on the 7th (Avastin 7th, placebo 7th) and 14th (Avastin 14th, placebo 14th) postoperative day. The anastomosis was resected and sent for histological study and for tissue biochemical assays (VEGF, endothelin-1 (ET-1), C-reactive protein (CRP), pro-oxidant-antioxidant balance (PAB), carbonylated proteins, hydroxyproline) using specific enzyme-linked immunosorbent assay kits. For statistical analysis, the Mann-Whitney U test was used (of statistical significance when P < 0.05).

RESULTS

No complication or anastomotic dehiscence was observed. Histology did not reveal statistically significant differences between groups concerning degree of inflammation, fibroblasts, collagen, and fibrosis. Likewise, hydroxyproline levels did not differ. However, some statistically significant differences were found in VEGF, CRP and carbonyl proteins (Avastin 7th vs placebo 7th, placebo 14th vs placebo 7th), ET-1, and PAB (Avastin 14th vs Avastin 7th), which did not finally affect the collagen synthesis marker hydroxyproline, nor did the anastomotic strength.

CONCLUSIONS

Bevacizumab, when administered intraoperatively, has no significant effect on colon anastomotic healing in rats despite a transient mild ischemia.

Human milk proteins: an interactomics and updated functional overview

Milk and milk fractions are characterized by a wide array of proteins, whose concentration spans across several orders of magnitude. By exploiting a combined approach based on functional gene ontology enrichment (FatiGO/Babelomics), hierarchical clustering, and pathway and network analyses, we merged data from literature dealing with protein-oriented studies on human milk. A total of 285 entries defined a nonredundant list upon comparison with the Ingenuity Knowledge Base from the Ingenuity Pathway Analysis software. Results were compared with an inventory of bovine milk proteins gathered from dedicated proteomic studies. A protein core of 106 proteins was found, with most of the entries associated to three main biological functions, namely nutrient transport/lipid metabolism, concretization of the immune system response and cellular proliferation processes. Our analyses confirm and emphasize that the biological role of the human milk proteins is not only limited to the provision of external nutrients and defense molecules against pathogens to the suckling but also to the direct stimulation of the growth of neonate tissues/organs and to the development of a proper independent immune system, both through the induction of a number of molecular cascades associated with cell proliferation/differentiation. The latter aspects were previously investigated by single-molecule dedicated studies, missing the holistic view that results from our analysis.

The bovine milk proteome: cherishing, nourishing and fostering molecular complexity. An interactomics and functional overview

Bovine milk represents an essential source of nutrients for lactating calves and a key raw material for human food preparations. A wealth of data are present in the literature dealing with massive proteomic analyses of milk fractions and independent targeted studies on specific groups of proteins, such as caseins, globulins, hormones and cytokines. In this study, we merged data from previous investigations to compile an exhaustive list of 573 non-redundant annotated protein entries. This inventory was exploited for integrated in silico studies, including functional GO term enrichment (FatiGO/Babelomics), multiple pathway and network analyses. As expected, most of the milk proteins were grouped under pathways/networks/ontologies referring to nutrient transport, lipid metabolism and objectification of the immune system response. Notably enough, another functional family was observed as the most statistically significant one, which included proteins involved in the induction of cellular proliferation processes as well as in anatomical and haematological system development. Although the latter function for bovine milk proteins has long been postulated, studies reported so far mainly focused on a handful of molecules and missed the whole overview resulting from an integrated holistic analysis. A preliminary map of the bovine milk proteins interactome was also built up, which will be refined in future as result of the widespread use of quantitative methods in protein interaction studies and consequent reduction of false-positives within associated databases.

The role and potential use of oral transforming growth factor-beta in the prevention of infant allergy

The increasing prevalence of allergic diseases in infants and children as well as adults has become an important issue in public health in industrial countries. However, few preventive measures are available to reduce the risk of allergic diseases in infants; e.g. the avoidance of smoking and alcohol consumption during pregnancy and lactation. Therefore, there is an enthusiasm to identify certain factors in foods, nutrients, and environment responsible for the primary prevention of allergic diseases during infancy. In the last decade, TGF-beta in maternal milk has been implicated in the prevention of allergic diseases in infants and young children. This review summarizes the relevant epidemiological reports and highlights the recent animal studies to support the preventive role of orally administered TGF-beta, such as TGF-beta in human milk, in the development of allergic diseases in infants. We also provide suggestions for the potential use of dietary (oral) TGF-beta for the primary prevention of allergic diseases. Further studies to address the scientific validity and mechanistic insight to this Mother Nature-inspired concept are clearly required and will be important to develop new approaches to prevent allergic diseases.

Transforming growth factor-beta activity in commercially available pasteurized cow milk provides protection against inflammation in mice

Cow milk contains a large amount of an immunoregulatory cytokine, transforming growth factor-beta (TGFbeta). The present study investigated whether commercially available pasteurized cow milk retains TGFbeta activity both in vitro and in vivo. Some commercial cow milk increased TGFbeta/Smad-responsive reporter activity and induced Smad2 phosphorylation and the transcription of the TGFbeta/Smad target genes TGFbeta itself and Smad7 in vitro. Mice treated orally with 500 microL of cow milk containing TGFbeta (3 microg/L) daily for 2 wk had increased phosphorylation of Smad2 and TGFbeta and Smad7 mRNA expression in the intestine. These mice also had significantly greater serum TGFbeta concentrations than the mice treated orally with PBS. Furthermore, oral administration of 500 microL of cow milk containing TGFbeta (3 microg/L) daily for 2 wk before the induction of dextran sodium sulfate colitis and lipopolysaccharide-induced endotoxemia ameliorated tissue damage and mortality, respectively, in mice. These in vivo effects of cow milk were abrogated by the simultaneous administration of TGFbeta type I receptor kinase inhibitor with the cow milk, and they were not observed after the oral administration of cow's milk containing little TGFbeta. In humans, 1 oral challenge of 10 mL/kg cow milk containing TGFbeta (3 microg/L) increased the plasma TGFbeta concentrations at 4 h after the challenge. Thus, some commercially available pasteurized cow milk retains TGFbeta activity, which may be able to provide protection against experimental colitis and endotoxemia associated with increased intestinal and circulating TGFbeta levels.

Biochemical mechanism of healing activity of the natural phenolic, allylpyrocatechol against indomethacin-induced gastric ulceration in mice

Indomethacin caused maximum stomach ulceration in mice on the 3rd day, which was associated with reduction of plasma total antioxidant status (TAS), COX-1, COX-2, mucosal PGE(2), VEGF, and vWF, along with an increase in endostatin levels. Treatment with the phytochemical allylpyrocatechol (5 mg/kg, p.o. for 3 days) provided significant ulcer healing by reversing these biochemical parameters, as well as increasing the EGF expression more than that observed due to ulceration. Omeprazole (3 mg/kg, p.o. for 3 days) provided a similar healing by improving TAS and mucin levels, without significantly altering the other parameters.

Host factors in amniotic fluid and breast milk that contribute to gut maturation

The gut represents a complex organ system with regional differences, which reflect selective digestive and absorptive functions that change constantly in response to bodily requirements and the outside milieu. As a barrier to the external environment, gut epithelium must be renewed rapidly and repeatedly. Growth and renewal of gut epithelial cells is dependent on controlled cell stimulation and proliferation by a number of signaling processes and agents, including gut peptides-both endogenous and exogenous sources. This cascade of events begins during fetal development; with the ingestion of amniotic fluid, this process is enhanced and continued during infancy and early childhood through the ingestion of human milk. Events influenced by amniotic fluid during fetal development and those influenced by human milk that unfold after birth and early childhood to render the gut mature are presented.

Healing properties of malabaricone B and malabaricone C, against indomethacin-induced gastric ulceration and mechanism of action

The healing activity of malabaricone B and malabaricone C, the major antioxidant constituents of the spice Myristica malabarica against the indomethacin-induced gastric ulceration in mice has been studied. The histological indices revealed maximum ulceration on the 3rd day after indomethacin administration, which was effectively healed by malabaricone B, malabaricone C (each 10 mg/kg body weight/day) and omeprazole (3 mg/kg body weight/day) for 3 days. Compared to the untreated ulcerated mice, treatment with malabaricone B, malabaricone C and omeprazole reduced the ulcer indices by 60.3% (P<0.01), 88.4% and 86.1% respectively (P<0.001). All the test samples accelerated ulcer healing than observed in natural recovery even after 7 days. Stomach ulceration reduced the total antioxidant status of plasma by 41% (P<0.05), which was significantly increased by malabaricone B (36%, P<0.01), malabaricone C (61%, P<0.001) and omeprazole (53%, P<0.001). Compared to the ulcerated untreated mice, those treated with malabaricone B reduced the levels of thiobarbituric acid reactive substances and protein carbonyls by 17% and approximately 34% respectively (P<0.05), while malabaricone C and omeprazole reduced the parameters almost equally (approximately 30%, P<0.01, and approximately 40%, P<0.01 respectively). Likewise, all the test samples reduced the oxidation of protein and non-protein thiols significantly (P<0.05). The antioxidant activity of the test samples could partly account their healing capacities. However, the differential potency of them was explainable by considering their relative abilities to modulate mucin secretion, PGE(2) synthesis and expression of EGF receptor and COX isoforms, malabaricone C being most effective in controlling all these factors.

Effects of epidermal growth factor on atrophic enteritis in piglets induced by experimental porcine epidemic diarrhoea virus

Epidermal growth factor (EGF) promotes gastrointestinal mucosal recovery by stimulating the mitogenic activity of intestinal crypt epithelial cells. The aim of this study was to determine the effects of EGF on atrophic enteritis induced in piglets by experimental infection with porcine epidemic diarrhoea virus (PEDV) strain Dr13. Two groups of 12 conventional, colostrum-deprived, 1-day-old, large White-Duroc cross breed piglets were inoculated orally with PEDV (3 x 10(5) 50% tissue culture infective doses), with or without EGF (10 microg/kg/day, intraperitoneally once daily for 4 days after infection) and compared to 12 uninfected, untreated control piglets. PEDV+EGF piglets had less severe clinical signs than PEDV only piglets at 48 and 60 h post-infection (hpi). Histologically, the ratio of villous height:crypt depth of PEDV+EGF piglets was significantly higher than PEDV only piglets at 36 and 48 hpi. Immunohistochemistry for Ki67 demonstrated increased proliferation in intestinal crypt epithelial cells of PEDV+EGF piglets compared to PEDV only piglets at 36, 48 and 60 hpi. EGF stimulates proliferation of intestinal crypt epithelial cells and promotes recovery from atrophic enteritis in PEDV-infected piglets.

Nutrition support in severe acute pancreatitis

Nutritional support can improve the outcome from severe acute pancreatitis in two ways: first by providing the building blocks for tissue repair and recovery, and second, by modulating the inflammatory response and preventing organ failure, both of which are responsible for most of the morbidity and mortality associated with the disease. This review discusses the evidence on which these statements are based.

Decreased human milk concentration of epidermal growth factor after preterm delivery of intrauterine growth-restricted newborns

BACKGROUND AND AIM

The aim of the study was to compare epidermal growth factor (EGF) concentration in 81 colostrum samples collected from mothers of newborns in the following growth categories: preterm appropriate for gestational age (AGA), preterm small for gestational age (SGA), and full term (FT).

RESULTS

Significantly higher concentrations of EGF were found in the colostrum of mothers who delivered premature AGA infants at less than 32 weeks of gestation compared with mothers who delivered premature SGA babies at the same gestational age.

CONCLUSIONS

We concluded that the maternal compensatory mechanism accelerating the development of immature breast-fed infants may be disturbed when gestation is complicated by intrauterine growth retardation.

Interleukin-22: a novel T- and NK-cell derived cytokine that regulates the biology of tissue cells

Interleukin (IL)-22, discovered in 2000, is a member of the IL-10 family of cytokines. The major sources of IL-22 are activated T1- and NK-cells. IL-22 acts via a heterodimeric receptor complex consisting of IL-22R1 and IL-10R2. Neither resting nor activated immune cells express IL-22R1 or respond to IL-22. In contrast, tissue cells at outer body barriers, i.e. of the skin, kidney, and the digestive and respiratory systems are targets of this cytokine. IL-22 functions by promoting the anti-microbial defense, protecting against damage, and re-organizing non-immune tissues. Furthermore, IL-22 induces acute phase reactants. These findings indicate that IL-22 represents a novel type of immune mediator that, although produced by immune cells, regulates tissue protection and homeostasis.

Intestinal Adaptation in Short Bowel Syndrome

Short bowel syndrome occurs when there is insufficient length of the small intestine to maintain adequate nutrition and/or hydration status without supplemental support. This syndrome most frequently occurs following extensive surgical resection of the intestine, and the extent of adaptation depends on the anatomy of the resected bowel and the amount of bowel remaining. Following resection, the intestinal tissue undergoes morphologic and functional changes to compensate for the lost function of the resected bowel. These changes are mediated by multiple interactive factors, including intraluminal and parenteral nutrients, gastrointestinal secretions, hormones, cytokines, and growth factors, many of which have been well characterized in animal models. The amount of small bowel remaining is the most important predictor of adaptive potential; neither structural nor functional adaptative changes have been demonstrated in humans or animal models with more extreme resections resulting in an end-jejunostomy. The current understanding of these processes has led to the recent use of supplemental hormones, such as growth hormone and glucagon-like peptide 2, in intestinal rehabilitation programs and may lead to the development of pharmacologic agents designed to augment the innate adaptive response.

Autocrine, paracrine and juxtacrine signaling by EGFR ligands

Receptor and cytoplasmic protein tyrosine kinases play prominent roles in the control of a range of cellular processes during embryonic development and in the regulation of many metabolic and physiological processes in a variety of tissues and organs. The epidermal growth factor receptor (EGFR) is a well-known and versatile signal transducer that has been highly conserved during evolution. It functions in a wide range of cellular processes, including cell fate determination, proliferation, cell migration and apoptosis. The number of ligands that can activate the EGF receptor has increased during evolution. These ligands are synthesized as membrane-anchored precursor forms that are later shed by metalloproteinase-dependent cleavage to generate soluble ligands. In certain circumstances the membrane anchored isoforms as well as soluble growth factors may also act as biologically active ligands; therefore depending on the circumstances these ligands may induce juxtacrine, autocrine, paracrine and/or endocrine signaling. In this review, we discuss the different ways that EGFR ligands can activate the receptor and the possible biological implications.

Mucosal repair and growth factors: recombinant human hepatocyte growth factor as an innovative therapy for inflammatory bowel disease

The repair of intestinal mucosal injuries is a tightly regulated process involving epithelial restitution, cell proliferation and maturation, and the dedifferentiation of epithelial cells. Deeper injuries also require additional repair mechanisms, including inflammatory processes, angiogenesis, and extracellular-matrix deposition. Once intestinal mucosal injury occurs, numerous growth factors and cytokines, including hepatocyte growth factor (HGF), keratinocyte growth factor, endothelial growth factor, epidermal growth factor, transforming growth factor-beta1, intestinal trefoil factor, interleukin (IL)-1, and IL-2, are induced in both the intestinal lumen and submucosa, and these factors cooperatively stimulate epithelial mucosal repair. HGF, a major agent promoting hepatocyte proliferation, also modulates intestinal epithelial cell proliferation and migration, leading to the acceleration of intestinal mucosal repair. Additionally, the proteolytic activation of HGF, which is mediated by HGF activator, is essential for the regeneration of injured intestinal mucosa. Recently, several studies have shown that the administration of recombinant human HGF or HGF gene therapy abrogates disease severity in several animal models of inflammatory bowel disease (IBD). Recombinant human HGF will soon be available for administration to patients with fulminant hepatic failure. Although additional preclinical biological studies are required, HGF has the potential to be an important new treatment modality promoting intestinal mucosal repair in patients with IBD.

Citocinas en la patogenia de la enfermedad celíaca

Celiac disease is manifested by an enteropathy caused by intolerance to gluten, a family of proteins found in wheat and other cereals. Following intestinal T-cell activation in predisposed individuals, different inflammatory mechanisms are triggered under the control of the cytokine balance including those with a pro-inflammatory Th1 pattern such as IFNgamma, TNFalpha, IL-15 and IL-18; and regulatory cytokines such as TGFbeta and IL-10. These cytokines, besides increasing the intensity of the activation and the number of immune cells within the intestinal mucosa, regulate the activity of epithelial growth factors and metalloproteinases, a group of molecules involved in the maintenance and turnover of the intestinal mucosa structure; in inflammatory conditions, they also induce the intestinal lesion responsible for malabsorption syndrome.

Intestinal adaptation after massive intestinal resection

Patients with short bowel syndrome require long term parenteral nutrition support. However, after massive intestinal resection the intestine undergoes adaptation and nutritional autonomy may be obtained. Given that the complications of parenteral nutrition may be life threatening or result in treatment failure and the need for intestinal transplantation, a more attractive option is to wean patients off nutrition support by optimising the adaptive process. The article examines the evidence that after extensive small bowel resection adaptation occurs in humans and focuses on the factors that influence adaptation and the strategies that have been used to optimise this process. The review is based on an English language Medline search with secondary references obtained from key articles. There is evidence that adaptation occurs in humans. Adaptation is a complex process that results in response to nutrient and non-nutrient stimuli. Successful and reproducible strategies to improve adaptation remain elusive despite an abundance of experimental data. Nevertheless given the low patient survival and quality of life associated with other treatments for irreversible intestinal failure it is imperative that clinical research continues into the optimisation of the adaptation.

Intestinal adaptation after massive intestinal resection

Patients with short bowel syndrome require long term parenteral nutrition support. However, after massive intestinal resection the intestine undergoes adaptation and nutritional autonomy may be obtained. Given that the complications of parenteral nutrition may be life threatening or result in treatment failure and the need for intestinal transplantation, a more attractive option is to wean patients off nutrition support by optimising the adaptive process. The article examines the evidence that after extensive small bowel resection adaptation occurs in humans and focuses on the factors that influence adaptation and the strategies that have been used to optimise this process. The review is based on an English language Medline search with secondary references obtained from key articles. There is evidence that adaptation occurs in humans. Adaptation is a complex process that results in response to nutrient and non-nutrient stimuli. Successful and reproducible strategies to improve adaptation remain elusive despite an abundance of experimental data. Nevertheless given the low patient survival and quality of life associated with other treatments for irreversible intestinal failure it is imperative that clinical research continues into the optimisation of the adaptation.

Hepatocyte growth factor facilitates the repair of large colonic ulcers in 2,4,6-trinitrobenzene sulfonic acid-induced colitis in rats

BACKGROUND

Hepatocyte growth factor (HGF) modulates intestinal epithelial cell proliferation and migration, serving as a critical regulator of intestinal wound healing. The aim of this study was to clarify the effects of administration of recombinant human HGF on colonic mucosal damage in vivo.

METHODS

Rats were given 7.5 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS) per rectum on day 0. On day 5, the degree of TNBS-induced colitis was evaluated endoscopically, and rats suffering from large ulcers (occupying more than two thirds of the luminal circumference) were treated with intravenous bolus injections of recombinant human HGF (1.0 mg/kg per day) or phosphate-buffered saline (PBS) for 5 days.

RESULTS

Rats with TNBS-induced colitis given human HGF showed a significant reduction in colonic ulcer coverage and large intestinal shortening compared with those treated with PBS. Administration of recombinant human HGF also stimulated the proliferation of epithelial cells and reduced the inflammatory cell infiltrate. Finally, HGF treatment decreased the myeloperoxidase activity and tumor necrosis factor alpha levels in the TNBS-inflamed colon tissues.

CONCLUSIONS

These results indicate that intravenous injection of HGF accelerates colonic mucosal repair and reduces infiltration of inflammatory cells in rats with TNBS-induced colitis and suggest that HGF has the potential to be a new therapeutic modality to promote intestinal mucosal repair in patients with inflammatory bowel disease.

The macrophage F4/80 receptor is required for the induction of antigen-specific efferent regulatory T cells in peripheral tolerance

We show that the mouse macrophage-restricted F4/80 protein is not required for the development and distribution of tissue macrophages but is involved in the generation of antigen-specific efferent regulatory T (T reg) cells that suppress antigen-specific immunity. In the in vivo anterior chamber (a.c.)–associated immune deviation (ACAID) model of peripheral tolerance, a.c. inoculation of antigen into F4/80^−/− mice was unable to induce efferent T reg cells and suppress delayed-type hypersensitivity (DTH) responses. Moreover, the use of anti-F4/80 mAb and F4/80^−/− APCs in an in vitro ACAID model showed that all APC cells in the culture must be able to express F4/80 protein if efferent T reg cells were to be generated. In a low-dose oral tolerance model, WT but not F4/80^−/− mice generated an efferent CD8⁺ T reg cell population that suppressed an antigen-specific DTH response. Peripheral tolerance was restored in F4/80^−/− mice by adoptive transfer of F4/80⁺ APCs in both peripheral tolerance models, indicating a central role for the F4/80 molecule in the generation of efferent CD8⁺ T reg cells.

Alanyl-glutamine hastens morphologic recovery from 5-fluorouracil-induced mucositis in mice

OBJECTIVE

In this study, we postulated the beneficial role of oral alanyl-glutamine, a more stable glutamine derivative to decrease 5-fluorouracil (5-FU)-induced mucositis in mice.

METHODS

We measured different morphologic parameters to assess structural changes over time in the small bowel, including crypt depth, villus height, villus area, mitotic and apoptotic indices at the crypt level using terminal deoxyuridine triphosphate nick end labeling, and hematoxylin-eosin staining of ileal tissue. In addition, we analyzed the effect of different alanyl-glutamine concentrations on animal weight curves after 5-FU treatment.

RESULTS

Neither glutamine nor alanyl- glutamine prevented the 5-FU intestinal structural damage or apoptosis in crypt enterocytes at 24 h after 5-FU challenge. However, we found that alanyl-glutamine, but not glutamine, speeds intestinal recovery when compared with 5-FU-treated controls (P < 0.05), predominantly by enhancing mitotic activity and crypt length.

CONCLUSION

Our findings provide important data to support clinical studies of oral alanyl-glutamine in 5-FU-induced mucositis.

Modulation of gastrin and epidermal growth factor by pyrrolizidine alkaloids obtained from Senecio brasiliensis in acute and chronic induced gastric ulcers

We investigated the antiulcerogenic activity of pyrrolizidine alkaloids (PAs) integerrimine, retrorsine, senecionine, usaramine and seneciplhylline, an alkaloidal extract obtained from Senecio brasiliensis. The PA extract demonstrated significantly activity in both, acute and chronic gastric ulcers on rats. The effects of PA extract were dose dependent. The mechanisms implicated on this activity were evaluated by determination of gastrin plasma levels in rats subjected to the acute treatment with PA extract and by expression of mRNA of Epidermal Growth Factor (EGF) after chronic treatment with this extract. The results showed that the PA extract increased both the levels of gastrin and the expression of EGF on these animals. Moreover, the histological examinations showed a reduction of exfoliation of superficial cells, hemorrhages and blood cell infiltration. We concluded that the PAs showed an important and qualitative antiulcerogenic activity mediated by increase in gastrin secretion and mRNA expression of EGF.

Genistein at a concentration present in soy infant formula inhibits Caco-2BBe cell proliferation by causing G2/M cell cycle arrest

Fifteen percent of all U.S. infants are fed soy formulas containing up to 47 mg/L of isoflavones (>65% as genistin + genistein); thus, these infants' intestines are exposed to a high dose of genistein, a phytoestrogen and tyrosine kinase inhibitor. Little attention has been focused on genistein's impact on the developing intestine. We hypothesized that a high dose of genistein would inhibit intestinal cell growth. Caco-2BBe human intestinal cells were exposed to 0, 3.7, and 111 micro mol/L (0, 1, and 30 mg/L) genistein in DMEM + 0.5% fetal bovine serum for 24-48 h. Cell number, thymidine incorporation, apoptosis, and cell cycle analyses were performed. The low genistein concentration increased intestinal cell proliferation by 28% (P = 0.001), but did not affect cell number or caspase-3 activity compared to the control. Furthermore, the addition of ICI, an estrogen receptor antagonist, negated the proliferative effect of the low genistein. In contrast, the high genistein concentration reduced cell number by 40%, proliferation by 94%, and caspase-3 activity by 50% compared to the control (P < 0.05). Cell cycle analysis after 48 h exposure to high genistein revealed 37% of cells in G0/G1 and 35% in G2/M vs. 71% in G0/G1 and 17% in G2/M for the control and low genistein groups. Thus, a biphasic effect of genistein was seen with a low dose stimulating intestinal cell proliferation through the estrogen receptor, whereas a high dose of genistein inhibited intestinal cell proliferation and altered cell cycle dynamics. A high dose of genistein may potentially compromise intestinal growth.

Role of cytokines in human intestinal villous development

Villous development of the intestine is beginning to be understood in terms of the underlying molecular mechanisms. There is increasing information on the role of cytokines as extrinsic regulators in this process. This article summarizes information available on various cytokines that have been studied in this context.

Reduction in heat-induced gastrointestinal hyperpermeability in rats by bovine colostrum and goat milk powders

Male Sprague-Dawley rats were assigned to one of three dietary groups [standard diet (Cont; n = 8), standard diet plus bovine colostrum powder (BColost 1.7 g/kg; n = 8), or goat milk powder (GMilk 1.7 g/kg; n = 8)] to determine the ability of these supplements to reduce gastrointestinal hyperpermeability induced by heat. Raising core body temperature of rats to 41.5 degrees C increased transfer of (51)Cr-EDTA from gut into blood 34-fold relative to the ambient temperature value (P < 0.05) in the Cont group of rats, indicative of increased gastrointestinal permeability. Significantly less (P < 0.01) (51)Cr-EDTA was transferred into the blood of rats in either the BColost (27% of Cont) or GMilk group (10% of Cont) after heating, showing that prior supplementation with either bovine colostrum or goat milk powder significantly reduced the impact of heat stress on gastrointestinal permeability. The changes in the BColost group were not significantly different than those of the GMilk group. The potential mechanism of the protective effect of bovine colostrum and goat milk powders may involve modulation of tight junction permeability, because both powders were able to maintain transepithelial resistance in Madin Darby canine kidney cells challenged with EGTA compared with cells maintained in media only. The results show that bovine colostrum powder can partially alleviate the effects of hyperthermia on gastrointestinal permeability in the intact animal. Moreover, goat milk powder was equally as effective as bovine colostrum powder, and both may be of benefit in other situations where gastrointestinal barrier function is compromised.

Hepatocyte growth factor facilitates colonic mucosal repair in experimental ulcerative colitis in rats

Hepatocyte growth factor (HGF) modulates intestinal epithelial cell proliferation and migration, serving as a critical regulator of intestinal wound healing. In this study, we examined the effect of administration of recombinant human HGF on colonic mucosal damage in vivo. Acute colitis was induced in rats by feeding with 5% dextran sulfate sodium (DSS) for 7 days, and colitis was subsequently maintained by feeding with 1% DSS. On the 5th day of DSS administration, osmotic pumps releasing recombinant human HGF (200 microg/day) were implanted into the peritoneum of the rats. Continuous intraperitoneal delivery of HGF led to both increased serum human HGF levels and c-Met tyrosine phosphorylation within the colonic mucosa. Compared with mock-treated rats, those administered human HGF showed a reduction in colitis-associated weight loss, large intestinal shortening, and improved colonic erosions. Enhanced epithelial regeneration and cellular proliferation were observed in rats treated with recombinant human HGF. The weights of the liver, kidneys, and spleen were not affected by HGF administration. These results indicate that HGF administration accelerates colonic mucosal repair in rats with DSS-induced colitis and suggest that recombinant human HGF may be a useful therapeutic tool to facilitate intestinal wound healing in patients with ulcerative colitis.

Toxicity of environmental lead and the influence of intestinal absorption in children

Exposure to metals, particularly lead, remains a widespread issue that is associated with historical and current industrial practices. Whereas the toxic properties of metals are well described, exposure to metals per se is only one of many factors contributing to elevated blood metal concentrations and their consequent health effects in humans. The absorbed dose of metal is affected by geochemical, biochemical, and physiological parameters that influence the rate and extent of absorption. In children, the interplay among these factors can be of critical importance, especially when biochemical and physiological processes might not have matured to their normal adult status. Such immaturity represents an elevated risk to metal-exposed children because they might be more susceptible to enhanced absorption, especially via the oral route. This review brings together the more recent findings on the physiological mechanisms of metal absorption, especially lead, and examines several models that can be useful in assessing the potential for metal uptake in children.

Preventive effect of hydrotalcite on gastric mucosal injury in rats induced by taurocholate

AIM: To study the preventive effect of hydrotalcite on gastric mucosal injury in rat induced by taurocholate, and to investigate the relationship between the protective mechanism of hydrotalcite and the expression of trefoil factor family 2 (TFF2) mRNA and c-fos protein.

METHODS: Forty five male Wistar rats were randomly divided into hydrotalcite group, ranitidine group and control group. Gastric mucosal injury was induced by introgastric acidified taurocholate. OD value of TFF2 mRNA expression in gastric mucous cells was determined by hybridization and computer image analysis system. OD value of c-fos protein expression in gastric mucous cells was measured by immunohistochemistry and computer image analysis system.

RESULTS: The gross mucosal injury index in hydrotalcite group was significantly lower than that in ranitidine group and control group (8.60 ± 2.20 vs 16.32 ± 4.27, 29.53 ± 5.39; P < 0.05, P < 0.01). The expression level of TFF2 mRNA in hydrotalcite group was markedly higher than that in ranitidine group and control group (0.56 ± 0.09 vs 0.30 ± 0.05, 0.28 ± 0.03, P < 0.05). The OD value of c-fos protein in hydrotalcite group was higher than that in ranitidine group and control group (0.52 ± 0.07 vs 0.31 ± 0.04, 0.32 ± 0.05, P < 0.05).

CONCLUSION: Hydrotalcite can protect gastric mucosal injury in rats induced by taurocholate, which may be related to the increased expression of TFF2 and c-fos protein.

Pharmacogenomic analysis of rhIL-11 treatment in the HLA-B27 rat model of inflammatory bowel disease

Recombinant human interleukin-11 (rhIL-11) reduces the clinical signs and histological lesions of inflammatory bowel disease (IBD) in transgenic rats expressing the human major histocompatability complex (MHC) class I allele, HLA-B27. To elucidate the pharmacogenomic effects of rhIL-11 in this model, we examined the global gene expression pattern in inflamed colonic tissue before and following rhIL-11 treatment using oligonucleotide microarrays. In total, 175 disease-related genes were identified. Increased expression of genes involved in antigen presentation, cell death and inflammation, and decreased expression of metabolic genes was associated with disease. A total of 27 disease-related genes returned to normal expression levels following rhIL-11 treatment including the MHC class II gene RT1-DMbeta. rhIL-11 induced the expression of four intestinal epithelial growth factors. These gene expression patterns indicate that treatment of inflammatory bowel disease with rhIL-11 affects class II antigen processing and colonic epithelial cell proliferation and metabolism.

Tolerance of simulated amniotic fluid in premature neonates

OBJECTIVE

To assess the tolerance of simulated amniotic fluid enterally administered in premature neonates.

DESIGN

A multicentered, Phase I, dose-escalation trial was accomplished among 30 preterm neonates. Groups of 10 patients received 5, 10, or 20 mL/kg/d enterally of the amniotic fluid solution, divided into every-3-hour dosing, for 3 days.

MAIN OUTCOME MEASURES

Amount and character of emesis, stools, and gastric residuals; changes in abdominal girth; presence of a skin rash; blood pressure instability; the diagnosis of necrotizing enterocolitis (NEC) or intestinal perforation.

RESULTS

Thirty patients were studied: 10 received 5 mL/kg/d, 10 received 10 mL/kg/d, and 10 received 20 mL/kg/d of amniotic solution. Gestational ages ranged from 25 to 31 weeks. The Data Safety and Monitoring Board met after each group of 10 patients completed the study, reviewed the outcome measurements, and recommended continuance of the study. Dosing was discontinued for 3 patients prior to receiving all 24 doses because of gastric residuals (n = 1; 5 mL/kg), stage I NEC (n = 1; 10 mL/kg), or symptomatic patent ductus arteriosus (n = 1; 20 mL/kg). The remaining patients completed the doses with no evidence of intolerance: specifically, no increased gastric residuals, increased abdominal girth, diarrhea, blood pressure change, rash, NEC, or intestinal perforation.

CONCLUSIONS

Enteral administration of an amniotic fluid-like solution to preterm neonates is well tolerated in doses <or=20 mL/kg/d.

Heparin-binding EGF-like growth factor (HB-EGF) decreases oxygen free radical production in vitro and in vivo

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been shown to protect intestinal epithelial cells from anoxia/reoxygenation in vitro, and to protect the intestines from ischemia/reperfusion (I/R) injury in vivo. The goal of the present study was to determine whether the cytoprotective effects of HB-EGF were due, in part, to its ability to decrease reactive oxygen species (ROS) production. Human whole blood, polymorphonuclear leukocytes, and monocytes, as well as rat intestinal epithelial cells, were exposed to stimuli designed to produce an oxidative burst in these cells. Treatment of the cells with HB-EGF led to a significant decrease in oxidative burst production. In vivo, total midgut I/R injury in rats led to increased ROS production, which was markedly decreased by HB-EGF treatment. Histochemically, I/R injury led to increased ROS production, which was significantly decreased with HB-EGF treatment. HB-EGF cytoprotection is due, in part, to its ability to decrease ROS production. Future studies will determine the mechanisms by which HB-EGF exerts these effects.

Distribution of epidermal growth factor receptor (EGFr) in normal and acute peptic-injured equine gastric squamous epithelium

Growth factors are important in healing and restoration of injured gastrointestinal tissues and, therefore, we characterised temporally the distribution and density of epidermal growth factor receptor (EGFr) in normal and peptic-injured gastric squamous epithelium of horses. Lesions were induced in the equine gastric squamous epithelium using a feed deprivation protocol that results in prolonged increased gastric acidity. Fifteen mature horses, 9 geldings and 6 mares, age 3 to 20 years, were used and divided into 3 groups: Group 1 (n = 5) were subjected to euthanasia for problems unrelated to the gastrointestinal tract and had normal-appearing gastric squamous mucosal epithelium; Groups 2 (n = 5) and 3 (n = 5) had lesions induced in the gastric squamous epithelium by alternating 24 h periods of feed deprivation and ad libitum access to hay, for a total of 48 h and 96 h, respectively. Following lethal injection of a barbiturate, stomachs were removed and fixed by filling with 4- 6 l 10% buffered formalin. Sections were made from normal stomachs and lesions in the gastric squamous epithelium adjacent to the margo plicatus along the right side of the stomach/greater curvature and the lesser curvature. A modified avidin-biotin immunoperoxidase technique was used to stain the formalin-fixed tissue specimens for EGFr. A computerised image analysis system was used to measure area occupied by EGFr (EGFr area) and mean EGFr density in 4 zones within the epithelium extending from the basal cell layers toward the lumen. Measurements were made of epithelium in an erosion bed, at the margin of an ulcer or erosion, and 10-15 mm distant from the lesion margin. Additionally, EGFr area and density were measured in epithelial cells adjacent to capillaries in the epithelium. Intermittent feed deprivation resulted in erosion and ulceration of the gastric squamous epithelium of each horse. Mean EGFr area and density were greatest (P<0.05) in the basal layer of epithelia from all horses, and EGFr staining diminished progressively toward the lumen. Tissues from Group 3 had significantly greater EGFr area in the lesion margin than epithelia from Group 2. EGFr density was less in the epithelia of erosion beds from Groups 2 and 3 compared to normal epithelium, and EGFr area in Group 2 erosion bed epithelia was significantly less than in normal epithelium and epithelia of Group 3. EGFr area in cells adjacent to epithelial capillaries of Group 3 was significantly greater than that of Group 1. Mitotic cell activity was significantly greater in epithelia associated with ulcers and erosions in Groups 2 and 3 compared to normal tissues from Group 1 horses. Staining for EGFr in the glandular mucosa adjacent to squamous epithelium at the margo plicatus was inconsistent and typically faint when present. EGFr distribution in equine gastric squamous epithelium was greatest in regions of greatest cell proliferation, and these areas were in the basal layers of epithelium and immediately adjacent to capillaries. There was evidence that EGFr is induced in peptic-injured equine gastric squamous epithelium. A receptor ligand, EGF or transforming growth factoralpha, may be a factor in healing of gastric squamous mucosal ulcers in horses. Further research should be directed at identifying this ligand and determining its origin in equine gastric mucosa.

Synergy between medical and nutrient therapies: George Washington meets Rodney Dangerfield

Although medical therapies are widely accepted by health practitioners, sometimes without adequate testing, nutritional therapy is frequently looked upon uniformly as without merit. There are many reasons for this attitude. However, a substantial body of literature has accumulated that objectively demonstrates the value of adding nutritional therapy to the prevention or treatment of some diseases or specific risk factors for diseases. Examples of successful nutrition therapy that can be combined with medical management include treatment of hypertension, hyperlipidemia, intermittent claudication, osteoporosis, respiratory distress syndrome, and arthritis.

Keratinocyte growth factor and coeliac disease

BACKGROUND

Coeliac disease is characterised by increased epithelial renewal associated with a mucosal T cell response to gliadin. Keratinocyte growth factor (KGF) is produced by cytokine activated gut stromal cells and may be a link between mucosal T cell activation in untreated coeliac disease and epithelial hyperplasia.

AIMS

To characterise expression of KGF in coeliac disease.

METHODS

KGF transcripts in coeliac disease were measured by quantitative competitive reverse transcription-polymerase chain reaction (RT-PCR) and localised using in situ hybridisation. KGF production by gluten reactive CD4+ T cell clones was examined. In addition, KGF transcripts were measured following ex vivo challenge of coeliac biopsies with a peptic-tryptic digest of gliadin.

RESULTS

KGF transcripts were elevated in coeliac biopsies compared with normal controls but were not different from non-coeliac disease controls. By in situ hybridisation, KGF mRNA containing cells were present in the upper half of the lamina propria, most abundantly just under the epithelium. There was no signal from cells within the epithelium. Gluten reactive T cell clones did not make KGF. In vitro challenge of coeliac biopsies generated a strong interferon gamma response but a specific KGF response could not be detected because of an extremely high number of KGF transcripts in all cultured biopsies.

CONCLUSIONS

KGF is overexpressed in coeliac biopsies and in tissues with non-coeliac enteropathy. No evidence was found for KGF production by intraepithelial lymphocytes or lamina propria T cells.

Peptide growth factors in the intestine

A continuously increasing number of regulatory peptides has been demonstrated to be expressed in the intestine and to modulate several functional properties of various intestinal cell populations, including the intestinal epithelium and lamina propria cell populations. These regulatory peptides include members of the epidermal growth factor (EGF) family, the transforming growth factor beta (TGF-beta) family, the insulin-like growth factor (IGF) family, the fibroblast growth factor (FGF) family, the trefoil factor (TFF) family, the colony-stimulating factor (CSF) family, and a few other seemingly unrelated regulatory peptides, such as hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF), and various interleukins, interferons and tumour necrosis factor-related proteins. In addition to the well-known effects on cell proliferation, these regulatory peptide factors regulate several other functional properties of epithelial and other cell populations, such as differentiation, migration, and extracellular matrix deposition and degradation. This review is designed not to discuss all the identified factors in detail but to highlight some of the basic principles of growth factor action in the intestine. It focuses mainly on classical growth factors rather than interleukins and interferons.

Mechanisms and modulation of intestinal epithelial repair

The mucosal epithelium of the alimentary tract represents a crucial barrier to a broad spectrum of noxious and immunogenic substances within the intestinal lumen. An impairment of the integrity of the mucosal epithelial barrier is observed in the course of various intestinal disorders including inflammatory bowel diseases (IBD), celiac disease, intestinal infections, and various other diseases. Furthermore, even under physiologic conditions temporary damage of the epithelial surface mucosa may be caused by proteases, residential flora, dietary compounds, or other factors. Generally, the integrity of the intestinal mucosal surface barrier is rapidly reestablished even after extensive destruction because of an enormous regenerative capability of the mucosal surface epithelium. Rapid resealing of the surface epithelium is accomplished by epithelial cell migration, also termed epithelial restitution, epithelial cell proliferation, and differentiation. Healing of the intestinal surface epithelium is regulated by a complex network of highly divergent factors, among them a broad spectrum of structurally distinct regulatory peptides that have been identified within the mucosa of the intestinal tract. These regulatory peptides, conventionally designated as growth factors and cytokines, play an essential role in regulating differential epithelial cell functions to preserve normal homeostasis and integrity of the intestinal mucosa. In addition, a number of other peptide molecules such as extracellular matrix factors and blood clotting factors, and also nonpeptide molecules including phospholipids, shortchain fatty acids, adenine nucleotides, trace elements, and pharmacological agents, have been demonstrated to modulate intestinal epithelial repair mechanisms. Some of these molecules may be released by platelets, adjacent stromal cells, inflammatory cells, or injured epithelial and nonepithelial cells and may play an important role in the modulation of intestinal injury. Repeated damage and injury of the intestinal surface are key features of various intestinal disorders including IBD and require constant repair of the epithelium. Enhancement of intestinal repair mechanisms by regulatory peptides or other modulatory factors may provide future approaches for the treatment of diseases that are characterized by injuries of the epithelial surface.